Photographic film assemblage and method for release of gas in diffusion transfer system

ABSTRACT

A photographic film unit comprising all of the materials required to produce a photographic print including a pair of sheets secured at their margins in face-to-face relation and a liquid processing agent; and a method of rapidly spreading a viscous liquid processing agent in a continuous uniform layer between the superposed sheets. A film unit is disclosed comprising a photosensitive sheet and a second sheet secured in face-to-face relation at the edges of the sheets by essentially fluidtight binding means adopted to release gas from between the sheets during spreading of the liquid carried in a collapsible container secured at one edge of the sheets so as to discharge its contents between the sheets when compressive pressure is applied to the container. A method is disclosed in which gas is discharged from between the sheets during spreading of the processing liquid therebetween and liquid is prevented from escaping by way of the means for releasing the gas.

PATENTEDUm 2e Isn 3,615,540 SHEET 1 0F 3 NVENTORS dfb/m ATTORNEYS' United States Patent [72] Inventors Edwin ll. Land Cambridge; Albert J. Bachelder, Lexington, both v Mass. [2l] AppLNo. 627,538 [22] Filed Mar.3l,l967 [45] Patented Oct. 26, 1971 [73] Assignee Polaroid Corporation Cambridge, Mass.

[54] PHOTOGRAPHIC FILM ASSEMBLAGE AND METHOD FOR RELEASE OF GAS IN DIFFUSION 2,686,716 8/1954 Land 96/76 Primary Examiner-Norman G. Torchin` Assistant Examiner-John J. Goodrow Attorneys-Brown and Mikulka and Robert E. Corb ABSTRACT: A photographic film unit comprising all of the materials required to produce a photographic print including a pair of sheets secured at their margins in face-to-face relation and a liquid processing agent; and a method of rapidly spreading a viscous liquid processing agent in a continuous uniform layer between the superposed sheets. A film unit is disclosed comprising a photosensitive sheet and a second sheet secured in face-toface relation at the edges of the sheets by essentially fluidtght binding means adopted to release gas from between the sheets during spreading of the liquid carried in a collapsible container secured atone edge of the sheets so as to discharge its contents between the sheets when compressive pressure is applied to the container. A method is disclosed in which gas is discharged from between the sheets during spreading of the processing liquid therebetween and liquid is prevented from escaping by way of the means for releasing the gas.

immuun-nah t .....IIIIII'In-Ill'l' PATENTEDUCT 26 |971l 3,61 5 54D SHEET 2 UF 3 INVENTORS v mm tl ,22ml

PAENEnnm 2s sn 3,615,540

sum a of s INVENTORS /4 p/rwl 5. ATTORNEYS process such as disclosed in the U.S. Pats. of Edwin H. Land, No. 2,543,181, granted Feb. 27, 1951 and No. 2,662,822, granted Dec. 15, 1953. In this embodiment, the film unit may comprise an image-recording medium including, as the photosensitive material, a silver halide emulsion; a liquid processing agent including a silver halide developer and a silver complexing agent; and the material required to provide a silver-precipitating environment in an image-receptive stratum of the film unit during processing. The processing liquid is distributed in contact with the layer containing the exposed image-recording medium for permeation therein to develop the latent image and form a soluble silver complex from unexposed silver halide which is transferred by diffusion to an image-receiving stratum where it is reduced to silver in the presence of a silver precipitant to form a visible positive image. The silver-precipitating environment may be provided initially as a layer or stratum on one of a pair of superimposed elements comprising the film unit, preferably an element different from the one including the image-recording medium, and/or the liquid composition distributed in a layer between the elements.

A preferred embodiment of the film unit of the invention includes all of the materials and reagents required to produce a full color photographic print by a process such as disclosed in U.S. Pat. No 2,983,606 issued May 9, 1961 in the name of Howard G. Rogers. This patent discloses a photosensitive element including a silver halide emulsion and a dye developer, that is, a dye which is a silver halide developing agent; a second or image-receiving element including an image-receiving layer of a dyeable material; and a processing liquid in which the dye developer is soluble. The photosensitive and image-receiving elements are superposed with the emulsion and image-receiving layers in face-to-face relation and the processing liquid is distributed in a uniform layer between and in contact therewith for permeation into the photosensitive layer where it initiates development of exposed silver halide. The dye developer is immobilized or precipitated in exposed areas as a consequence of development while in unexposed areas and partially exposed areas of the emulsion, the dye developer remains unreacted and diffusible thereby providing an imagewise distribution of unoxidized dye developer which is transferred, at least in part, by diffusion to the image-receiving layer without altering the imagewise distribution of the dye developer, to form a reversed or positive color image of the developed latent image in the emulsion. Multicolor transfer images are obtained utilizing dye developers, for example, by employing an integral multilayer photosensitive element such as illustrated in FIG. 9 of the U.S. Pat. No. 2,983,606 including at least two selectively sensitized overlying photosensitive strata on a single support. A typical photosensitive element of this type comprises a support carrying a red-sensitive silver halide emulsion stratum, a green-sensitive silver halide emulsion stratum and a blue-sensitive silver halide emulsion stratum, the emulsions having associated therewith, respectively, for example, a cyan developer, a magenta dye developer and a yellow dye developer. Each set of silver halide emulsion and associated dye developer strata may be separated from other sets by suitable interlayers formed, for example, of gelatin or polyvinyl alcohol. ln the example given, the dye developers are preferably selected for their ability to provide colors useful in producing a full color image by a subtractive process and may be incorportated in the respective silver halide emulsion with which they are associated or in a separate layer behind their respective silver halide emulsion. ln certain instances, a yellow filter is incorporated located in front of the green-sensitive emulsion and comprising a yellow dye developer or a separate layer of a yellow filter material.

`Reference is now made to FIGS. l through of the drawings wherein there is illustrated a photographic film unit l0 embodying the invention, the thickness of the materials being exaggerated for purposes of clarity of illustration. Film unit l0 comprises a photosensitive or image-recording sheet l2, a second or image-receiving sheet 14 and a rupturable container 16 holding a quantity of processing liquid 18. Sheets l2 and 14 are preferably rectangular and coextensive with one another and are arranged in superposed face-to-face contact with at least one edge of each sheet aligned with an edge of the other. The two sheets are retained in superposed relation by abinding element 20 in the form of a rectangular sheet larger than either of the photosensitive or image-receiving sheets and secured to the two sheets at the margins thereof. Binding element 20 is in the general form of aframe having a large rectangular opening 22 defining the extent of `the image produced in the film unit, surrounded by lateral edge portions 24 and end portions 26 and 28. Sheet l2 includes lateral marginal portions 30 and an end marginal portion 34 and sheet 14 includes lateral marginal portions 32 and an end marginal portion 36 with the lateral and end marginal portions of the two sheets being located in face-toface contact, preferably with the edges thereof in alignment. The lateral edge portions 24 and end portion 26 of binding element 20 are secured around and to, respectively, lateral marginal portions 30 and 32 of sheets 12 and 14 and end marginal portions 34 and 36 of the sheets effectively binding the two sheets to one another along three sides thereof. In a preferred form of film unit adapted to produce a reflection print surrounded by a white border and viewed against a white background, at least binding element 20 is formed of an opaque, white material and container 16 may also include a white outer coating to provide a more aesthetically pleasing product.

Container 16 is of the type shown in U.S. Pat. No. 2,543,181, formed by folding a rectangular blank of a fluidimpervious sheet material medially and sealing the marginal sections of the black to one another to form a cavity for containing processing liquid 18. The seal between longitudinal marginal sections 38 of the container is weaker than the end seals so that upon the application of a predetermined compressive force to the walls of the container in the region of the liquid-filled cavity, there will be generated within the liquid hydraulic pressure sufficient to separate longitudinal marginal sections 38 throughout the major portion of their length to form a discharge mouth at least equal in length to the length of the cavity and the width of opening 22 through which processing liquid 18 is discharged. Container 16 is attached to the sheets at the edges thereof opposite end portions 34 andl 36, preferably with the longitudinal edge of the container butted against the edges of the sheets and with the discharge passage of the container aligned with the facing surfaces of the sheets. Sheets 12 and 14 include, respectively, end marginal portions 40 and 42 and-the means for coupling the container to the sheets include end portion 28 of binding element 20 secured to end marginal portion 42 of sheet 14 and longitudinal marginal sections 38 of the container so as yto bridge the container and sheet 14; and a strip 44 secured to end marginal portion 40 of sheet 12 and the other longitudinal marginal section 38 of the container to bridge the gap between the container and sheet 12. The binding element andstrip 44 cooperate to provide a liquidtight seal between-the marginal sections of the container defining the discharge mouth thereof and sheets 12 and 14; and form a conduit'for conducting the liquid from the container between the sheets at end marginal portions 40 and 42 thereof.

The most useful and advantageous film unit insofar as packaging, storing, handling, exposure and processing are concerned, is one characterized by an integral, unitary structure constructed so that its integrity may be maintained during and after exposure and processing; and a structure that is sturdy, has some flexibilty andcan be handled and manipulated by mechanical means without damage to produce a useful and attractive photographic print. A useful and attractive photographic print can be described as being substantially flat or planar and without a tendency to curl as the result of the tem` perature and humidity changes; as being relatively rigid and inflexible as opposed to being limp or easily bent; as having a uniform white border surrounding a well-def`|ned rectangular image that extends to the border; and a protective coating or PHOTOGRAVPHIC FILM ASSEMBLAGE AND METHOD FOR RELEASE F GAS IN DIFFUSION TRANSFER SYSTEM The film unit of the invention is adapted to be employed in and the process of the invention is adapted to be performed by a self-developing camera of the type in which a completely, self-contained film unit is exposed and then processed by moving it relatively rapidly between a pair of pressure-applying members. The components of the film unit are assembled together to form an integral structure and the integrity of this structure is maintained during exposure and processing, thereby making it unnecessary to store, handle and/or move separately, individual elements of the film unit and minimizing the complexity of the structure required to contain and manipulate the film unit to effect exposure and processing thereof. Further reduction in the complexity of the exposure and processing mechanisms of the camera can be realized by combining the functions of components of the apparatus, specifically, by exposing the film unit during movement thereof bythe processing means which may comprise a pair of pressure rollers. This type of exposure and processing system necessitates movement of the film unit during processing at a speed that is relatively rapid, e.g., of the order of 9 inches per second, is accurately predetermined, is governed within relatively narrow limits. A film unit structure that is attractive, includes a minimum of simple and easily assembled components, is of a minimum size in relation to image size and generally includes substantially no excess materials, includes the processing liquid and means for promoting and facilitating spreading of the liquid in a layer of predetermined depth and extent, is inexpensive and functions reliably well, described in thecopending U.S. Pat. applications of E. H. Land, Ser. No. 622,287 and E. l-l. Land, et al., Ser. No 622,286, `both filed Mar. l0, 1967, These applications also disclose a method ofprocessing a film unit of this type enabling the rapid and accurate spreading of a predetermined quantity of a viscous processing liquid in a layer of uniform depth completely over an area between two sheets without entraining air in the liquid while generally avoiding discontinuities in the liquid that might otherwise detract from an attractive, positive photographic print.

The sheets of the film unit are secured to one another to form an essentially sealed structure preferably containing a minimum of air or other gas. During processing, the viscous liquid is spread from the leading end of the film unit between the sheets toward the trailing end thereof to form a layer between the sheets and any air between the sheets is advanced toward the trailing ends of the sheets ahead of the processing liquid. Excess processing liquid is trapped and retained within the film unit at the trailing end thereof, however, air within the film may interfere with rapid spread of the processing liquid and/or become trapped within the film unit at the trailing end thereof. Air trapped within the film unit tends to become compressed during spreading of the processing liquid and may thereafter cause separation of the sheets or otherwise damage the finished image.

An object of the invention is to provide a film unit structure of the type described including novel and improved means for venting gas from the film unit so that it does not interfere with spreading ofthe processing liquid within the film unit.

Another object of the invention is to provide a film unit structure and method of processing the film unit in which provision is made for rapidly releasing gas from the film unit during spreading of the processing liquid while preventing escape of the processing liquid.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The film unit of the invention generally comprises two separate, flexible sheetlike elements including a first or imagerecording sheet including a layer containing a photosensitive image-recording material and a second or image-receptive sheet for aiding in the distribution of a viscous liquid processing agent as a layer in contact with an exposed area of the photosensitive material and for acting as a support for a transfer image formed by diffusion of image-forming substances from the photosensitive material-containing layer through the layer of processing liquid to the second sheet. At least one of the sheets, preferably the second sheet, is transparent to provide for exposure of the photosen'sitive material while the sheets are in superposition and viewing of the image formed against the inner surface of the second sheet. This construction enables the two sheets to be secured to one another at their margins to form an integral unit, the integrity of which is established prior to loading into a camera, is maintained throughout exposure and processing and can be maintained subsequent to processing. The processing liquid includes, in addition to the reagents required to produce a diffusion transfer image, a thickening or film-forming agent provided to aid in the formation of a layer or film of the liquid between sheets and an opacifying agent for masking a visible (negative) image formed in the photosensitive layer and providing a background for the diffusion transfer (positive) image formed against the inner surface of the transparent second sheet.

Film units of this general type are described, for example, in U.S. Pats. of Edwin H. Land, No 2,873,658, granted Feb. 17, 1959, and No. 3,053,659, granted Sept. I l, i962. These patents show structure similar to the film unit of the invention insofar as they include image-recording and image-receptive layers and containers of viscous processing liquid located externally of the elements. The film unit of the present invention is distinguished by a novel combination of features that fulfill the objectives of the invention particularly with regard to the achievement of an integral two-sheet film unit and container that is easy to store and handle before, during and after exposure and processing, the rapid spreading of the processing liquid without entraining air to produce a uniform layer of accurately predetermined thickness and the production of an attractive finished photographic print comprising a film unit, the integrity of which is maintained throughout and following exposure and processing.

The invention accordingly comprises the apparatus possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:

FIG. l is a perspective view, partially in section, of a photographic film unit embodying the invention;

FIG. 2 is a longitudinal, sectional view showing the film unit of FIG. l and a step in the process employing the film unit;

FIG. 3 is a transverse sectional view of the film unit illustrating a step in the process, the section being taken substantially along the line 3--3 of FIG. 2;

FIG. 4 is an exploded projective view of components of the film unit;

FIG. 5 is a plan view of the trailing end portion of the film unit;

FIGS. 6 and 7 are sectional views taken substantially along the line 6--6 of FIG. 5 illustrating steps of the method employing the film unit.

The film unit and method of the invention are adapted to the performance of a number of different image-forming processes and particularly to the production of a positive photographic print preferably in full color produced by a diffusion-transfer process in which a photographic image-recording medium including a photosensitive material such as silver halide is exposed to form an image (latent) therein and is treated by wetting with a liquid processing agent to develop the image in the image-recording medium, form an imagewise distribution of transferable image-forming substances and transfer the image-forming substances by diffusion to an `image-receptive stratum in which they are immobilized to form a visible positive image. The film unit may comprise materials for producing a black-and-white print according to a covering for the image permitting the print to be handled and stored without the necessity for taking special precautions to avoid damage and deterioration. The structure and composition of components of the film unit of the invention combine to provide a film unit meeting these criteria, and together with the steps involved in the process of the invention, are specially adapted to provide a useful and attractive photographic print, preferably in full color, having the foregoing characteristics.

In order to provide a rigid durable structure having an integrity which is maintained from the time of assembly (during manufacture) to the finished print and providing a protective environment for the photosensitive medium as well as the final image, while permitting exposure of the photosensitive medium and viewing of the final image, at least one of the sheets of the film unit is formed of a transparent material. ln the embodiment shown in the drawings, the second or image-receiving sheet is transparent and the photosensitive medium is exposed and the final image is viewed through the image-receiving sheet which functions to protect both the image-recording medium and the final image. In other embodiments of the film unit the photosensitive sheet may be transparent depending upon the manner in which the image-recording medium is exposed and the final image is formed and viewed. The transparent image-receiving sheet may be formed of a conventional film -base material such as cellulose triacetate coated on its inner surface with one or more layers providing an appropriate environment for the formation of a diffusion transfer image. ln a film unit designed to produce a color image in terms of' a dye developer, the image-receiving sheet may be prepared as disclosed in the following example, by coating a transparent cellulose triacetate film base in succession with the following layers:

l. the partial butyl ester of polyethylene/maleic anhydride copolymer prepared by refluxing, for 14 hours, 300 grams of high-viscosity poly- (ethylene/maleic anhydride), 140 grams of n-butyl alcohol and 1 cc. of 85 percent phosphoric acid to provide a polymeric acid layer approximately 0.75 mils. thick;

`2. a solution of hydroxypropyl cellulose in water to provide a polymeric spacer layer approximately 0.075 mils. thick; and

3. a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4- vinylpryidine, at a coverage of approximately 600 mgs./ft.2, to provide a polymeric image-receiving layer approximately 0.40 mils. thick.

In a Vpreferred embodiment of the film unit useful in color photography and incorporating an image-receiving sheet prepared as described above, the image-recording sheet is preferably opaque to actinic light and is prepared by coating a succession on a gelatin subbed opaque cellulose triacetate film base.

The image-recording and image-receiving elements may incorporate other strata and coatings commonly employed in photographic products of this type such as optical coatings for preventing halation and reflection and otherwise improve the optical properties of the sheet material and to facilitate and improve exposure and viewing of the final image. For further details and examples of the composition and structure of image-recording and image-receiving sheets suitable for incorporation in the film unit of the invention, reference may be had to the copending U.S. Pat. Application of Edwin H. Land, entitled PHOTOGRAPHIC PRODUCTS AND PROCESSES, filed on an even date herewith as a continuation-impart of U.S. Pat. application Ser. No. 234,864, filed Nov. l, 1962, now Pat. No. 3,362,819, granted Jan. 9, 1968.

The embodiment of the film unit illustrated and described lherein is adapted to be exposed and processed to produce a multicolor dye transfer image in a dyeable polymeric layer located between a transparent film on which the dyeable polymeric layer is supported and an opaque layer located between the image and the photosensitive medium. This opaque layer comprises the liquid contents 18 of container 16 provided in sufficient quantity to form a layer of predetermined thickness, e.g. of the order of 0.004 inch, when disl tributed uniformly between the sheets over an area at least coextensive with opening 22 in binding element 20. The quantity of' liquid 18 supplied in the container is preferably just sufficient to form a layer of the desired thickness and extent thereby making it unnecessary to provide means for collecting and retaining excess processing liquid and also providing for minimizing the size, quantity and complexity of the container, its contents and the other components of the film unit. The processing liquid contained in container 16 comprises an aqueous alkaline solution having a pH at which the dye developers are soluble and diffusible and contains an opacifying agent in a quantity sufficient to mask the dye developers retained in the image-recording layer (laminate) subsequent to processing; and a film-forming viscosity increasing agent or agents to facilitate rupture of the container and distribution of the liquid processing composition and help in maintaining the layer of processing composition as a structurally stable layer tending to bind the sheets to one another.

As a general rule, the opacifying agent will be present in the layer of liquid spread between the transparent image-receiving sheet and the opaque image-recording sheet in a concentration sufficient to prevent further exposure of the imagerecording medium by actinic radiation transmitted by the transparent image-receiving sheet. Because the silver halide emulsion or emulsions comprising the image-recording strata are thus protected against exposure by incident actinic radiation at one major surface by the opaquefprocessing composition and at the remaining major surface by the opaque support sheet, it is possible to process the film unit subsequent to distribution of the liquid processing composition in the presence of actinic radiation and thereby eliminate the need to provide a processing chamber within the camera and/or make it possible to withdraw the film unit from the camera almost immediately following distribution of the processing liquid. Binding element 20, strip 44 and the material comprising container 16 are also formed of a material opaque to actinic radiation to prevent exposure of' the image-recording medium. The opacifying agent is selected for its suitability as a background for viewing the dye-transfer image formed in the dyeable polymeric layer as well as for its opaque property. Another factor considered in the selection of the opacifying agent is the requirement that it does not interfere with the formation and color integrity of the dye-transfer image in the image-receiving sheet and that the agent be aesthetically pleasing and does not provide a noisy background that may degrade the image or detract from the information content thereof. Opacifying agents particularly desirable for incorporation in the liquid processing composition are those providing a white background for viewing the transfer image and particularly those compositions conventionally employed to provide a background for photographic reflection prints and having optical properties particularly suited for the reflection of incident radiation.

As examples of suitable opacifying agents mention may be made of barium sulfate, zinc oxide, titanium dioxide, barium stearate, silver flake, silicates, alumina, zirconium oxide, zirconium acetyl acetate, sodium zirconium sulfate, kaolin, mica and the like. An opacifying agent especially preferred because of its high reflection properties is titanium dioxide and where it is desired to increase the opaqueness of the processing cornposition containing, for example, titanium dioxide, beyond that ordinarily obtained, and additional opacifying agent such as carbon black may be added in a concentration of about one part carbon black to -500 parts titanium dioxide. A liquid processing composition suitable for incorporation in container 16 for use in combination with sheet materials of the type disclosed in the foregoing example is as follows:

Water 100.0 cc. Potassium Hydroxide 1 1.2 grams Hydroxyethyl cellulose (high 3.4 grams viscosity) [commercially available from Hercules Powder Co.. Wilmington. Del..

under the trade name Nntrasol 250] N-benzyl-a-picolinium bromide l.5 grams Benzotriazole l.0 grams v gram dioxide 40,0 grams Reference may be had to the aforementioned copending application for additional details and examples of liquid processing compositions adapted for incorporation of the invention to effect the process thereof.

Subsequent to exposure, film unit 10 is processed as illustrated in FIG. 2 of the drawings, by moving the film unit with container 16 foremost relative to and between a pair of juxtaposed members for applying compressive pressure first to the container to eject the fluid contents of the container between the photosensitive and image-recording sheets l2 and 14 and thenspread processing liquid 18 in a uniform, thin layer between sheets over an area at least coextensive with opening 22 in binding element 20. As previously noted, the processing liquid includes an agent for increasing the viscosity of the liquid so as to promote opening of the discharge passage of the container throughout substantially its entire length and facilitate the discharge of the liquid from the container and spreading of the liquid between the sheets. For this purpose, the liquid should be quite viscous and contain the film-forming material in quantities sufficient to impart a viscosity in excess of 1,000 centipoises at a temperature of C., and preferably of the order of 1,000 to 200,000 centipoises at said temperature.

Preferred means for spreading the processing liquid in a thin layer of uniform predetermined thickness comprise a pair of cylindrical rolls 46 mounted in juxtaposition for rotation about axes located in a common plane and biased toward one another and/or mounted a fixed maximum distance apart so as to apply compressive pressure to the container and elements of the film unit during movement thereof between the rolls. During movement of the film unit between rolls 46, compressive pressure is initially applied to container 16 generating hydraulic pressure in liquid 18 effecting the rupture of the bond betweenl longitudinal marginal sections 38 of the con tainer and the discharge of liquid 18 in the form of an elongated mass between sheets 12 and 14 at end marginal portions 40 and 42 thereof as shown in FIG. 2. Continued movement of the film unit relative to and between spread rolls 46 causes advancement of the mass of liquid between the sheets toward the opposite end thereof and spreading of the liquid as a thin layer 48 of predetermined thickness between and in contact with the facing surfaces of the sheets. A number of expedients are possible for controlling the thickness of the layer of processing liquid distributed between sheets including means in the processing apparatus for appropriately gapping or spacing apart spread rolls 46 and/or components of the film unit capable of performing this function. The film unit illustrated in the drawings is adapted to be employed with cylindrical rolls with the thickness of the liquid layer 48 being controlled, as illustrated in FIGS. 2 and 6, by components of the film unit itself. The spacing between spread rolls 46 and hence the thickness of the layer of processing liquid is determined by the thickness of the film unit at the lateral margins thereof. This thickness is in turn a function of the thickness of the photosensitive and second sheets l2 and 14 and the thickness of lateral edge portions 24 of binding element 20. Since the photosensitive and second sheets are of substantially uniform thickness throughout, the thickness of layer 48 of processing liquid is determined by the thickness of binding element 20 and is approximately twice the thickness-of the binding element. In a typical film unit, for example, the binding element may have a thickness of the order of 0.002 inch and provide for spreading of the processing liquid in a layer having an initial depth of the order of 0.004 inch.

To insure spreading of the processing liquid to the edges of Y the area defined by opening 22 in the binding element and formation of a transfer image extending to the edges of this area, image-receiving sheet 14 is embossed at its margins to displace marginal portions 32, 36 and 42 out ofthe place of the medial portion of sheet 14 toward sheet l2 by a distance or depth approximating the thickness of binding element 20 or, one-half of the desired initial thickness of the layer of processing liquid; This construction, shown in FIGS. 2, 3 and 4, provides for the formation of a layer of processing liquid extending substantially to the lateral edges of opening 22 in the binding element. To further insure the formation of a layer of processing liquid extending at least to the lateral edges of the opening in the binding element, the edge sections of lateral edge portions 24 and end portion 28 secured to marginal portions 32 and end portion 36 of sheet 14 are wider than the sections of lateral edge portions 24 and end portion 28 secured to marginal portions 30 and end portion 34 of sheet l2. Strip 44 is also narrower than end portion 26 and as a result of this construction shown in FIGS. 2, 3, 6 and 7, during spreading of the processing liquid between sheets l2 and 14, the inner surfaces of the sheets will be spaced apart in lateral and end regions extending outside ofthe edges of opening 22 allowing processing liquid to enter these regions (see FIG. 3) and provide a reservoir of liquid for effecting image-fomation within the region ofthe exposed image-recording medium immediately adjacent the lateral and end edges of opening 22. The processing liquid is initially spread as shown in FIGS. 3 and 6 in a layer having a depth approximately twice the thickness of the binding element and calculated to provide aqueous liquid sufficient to permeate the layer containing the photosensitive medium and effect formation of a diffusion transfer image. As the liquid permeates the photosensitive layer and is absorbed and/or dissipated by sheets l2 and 14, the thickness of layer 48 is reduced and the film-forming agent becomes increasingly solid to provide a dimensionally stable opaque layer providing a background for the transfer image and tending to adhere the sheets to one another to preserve the integrity of the film unit structure. The depth of embossing of image-receiving sheet 14 approximates the final thickness of layer 48 lo provide an integral laminated assembly of substantially uniform thickness throughout in which layer 48 and the image extend to the edges of opening 22 in binding element 20.

As previously noted, the film unit of the invention is especially designed to be processed rapidly, that is, to be moved at a relatively high linear rate (e.g., nine inches per second) between spread rolls 46 to distribute the processing liquid in a layer that is continuous, is of uniform depth and extends throughout the entire area within opening 22 of binding element 20. These constraints together with the desirability of providing a minimum of processing liquid in excess ofthe precise amount of processing liquid required to produce the liquid layer, create substantial problems insofar as spreading of the liquid is concerned. During spreading, liquid 18 is advanced between the sheets as a mass located immediately ahead of spread rolls 46 and extending from side-to-side of the region defined by opening 22. It has been found that air (or any gas) located between the sheets during spreading of the processing liquid has an adverse e'ect because it tends to become entrained as air bubbles in the rapidly advancing mass of liquid and the bubbles form voids or discontinuities in the layer of liquid; and additionally, this air between the sheets must be advanced ahead of the mass of liquid and tends to inhibit the advancement of the mass of liquid behind the mass of air. However, if the sheets are initially disposed in face-to-face Contact throughout the major portion of the region in which the liquid is to be distributed as a layer and a substantial quantity of air is excluded from this region between the sheets, air entrainment is prevented and spreading of the liquid is facilitated because it is unnecessary to advance a mass of air ahead of the processing liquid.

It is important to the prevention of air entrainment and the facilitation of spreading that air be excluded from between sheets immediately ahead of the advancing mass of processing liquid and for this purpose, the processing apparatus is provided with a second pair of pressure applying mer'nbers shown in FIG. 6 as a pair of juxtaposed rolls 50 located ahead of rolls 46 and spaced therefrom by a distance approximately equal to or slightly greater than the width of the advancing mass of processing liquid so that as the lm unit is advanced between rolls 46 to spread the processing liquid, rolls 50 press sheets 12 and 14 into face-to-face contact immediately ahead of the mass of advancing liquid excluding air from between the sheets at least in the region thereof between the rolls. Rolls 50 may perform an additional function of distributing the mass of liquid laterally to insure formation of a liquid layer extending into the comers of opening 22 at the end thereof furthest from container 16. Rolls 50 are spaced from rolls 46 by a distance atleast equal to the width of the fluid-filled cavity of container 16 so .that rolls 50 do not inhibit the rupture of the container and the discharge of lits fluid contents by compressing marginal sections 38 of the container holding the discharge mouth closed while the container is being compressed by rolls 46 to effect discharge of its liquid contents.

lt is desirable, in a film unit of the type embodying the invention, to limit the processing liquid provided in the container as closely as possible to the precise amount required to provide a layer of the desired depth over the region between the sheets defined by opening 22 in binding element 20. However, in order to insure distribution of the liquid in a layer of uniform predetermined depth over the entire exposed region to the trailing end thereof and allow some tolerance in the manufacture and filling of the container as well as the depth of the layer of liquid, it is usually necessary to provide some excess processing liquid. This makes it necessary to provide for collecting and retaining the excess processing liquid within the film unit at the trailing end thereof so the liquid does not escape and contaminate the apparatus, e.g., camera, in which the film unit is processed. Collection and retention of the processing liquid is accomplished by providing spaces within the film unit in which the processing liquid is trapped or collected and from which the processing liquid cannot be squeezed by the pressure-applying lmembers employed to spread the liquid.

ln a preferred form of film unit shown in the drawings, liquid trapping and retaining spaces are defined by the openings in the trailing end marginal portions of either or both of the sheets underlying end portion 28 of binding element 20. In the form shown in F IGS. 4 and 7, openings 54 are provided in end marginal portion 36 of sheet 14 for collecting and retaining excess processing liquid as it is spread toward the trailing edge of the film unit beyond the trailing edge of opening 22. Thus, as shown inFlGS. 6 and 7, the advancing mass of processing liquid 18 separates the trailing end marginal portions of the sheets sufficiently to enable the excess processing liquid to enter openings 54 while the thickness of sheet 14 precludes compression of the trapped liquid so that there is little or no force tending to eject the liquid from the film unit. Retention of the processing liquid within the filmV unit is further assured by virtue of end portion 28 of binding element which is secured to the outer surfaces of end marginal portions 34 and 36 of sheets l2 and 14 respectively, and particularly in the regions of sheet 14 surrounding openings 54. As rolls 46 pass over the end marginal portions of the sheets and opening 54, the rolls are spaced apart by the removing sections of sheet 14 so that spaces defined by the binding element sheet 12, and the edges of openings 54 are provided -for trapping and retaining the excess processing liquid.

Entrainment of air in the liquid is prevented and spreading is effected by excluding as much as possible of the air from between the sheets, particularly in the region between the sheets immediately ahead of the mass of liquid during spreading of the liquid. Binding element 20 and strip 44 are preferably formed of a substantially liquid impermeable material which, in one form, e.g., a polymeric film, waterproof paper or the like, is also essentially impermeable to gas. While the film unit may be assembled in an ambient atmosphere and substantially all air excluded from between the sheets by pressing the sheets into face-to-face contact throughout sub stantially the entire area of the facing surface before securing the sheets to one another and to the container with binding element 20 and strip 44, it is difficult to exclude all gas (air) from the film unit during manufacture and, unless the binding element and strip 44 are adhered to the sheets in such a way as to substantially prevent the entry of air, air may enter the film unit during exposure and storage.

It is important in order to facilitate spreading of the processing liquid and prevent entrainment of air in the processing liquid, to exclude as much as possible of the air from between the sheets ahead of the mass of liquid during spreading thereof; and since there may be some air between the sheets, it is also necessary to provide for venting or otherwise expelling the air from between the sheets without inhibiting the spreading of the processing liquid while at the same time preventing the processing liquid for escaping between sheets. Escape of the processing liquid from between the sheets is effectively prevented by the provision of trapping spaces and a liquidtight retaining element secured to the outer surfaces of the sheets. It has been found that such an element inhibits or prevents escape of air from between the sheets and that any air thus trapped between the sheets at the training end thereof tends to become compressed during spreading of the processing liquid and may thereafter expand toward the -leading end of the film unit causing separation of the sheets and damage tothe visible image formed between the sheets.

In accordance with one of the subjects of the invention, a film unit construction is provided for venting a film unit in such a way as not to inhibit the release or escape of air, while at the same time preventing the processing liquid from escaping from the film unit. A preferred means for venting the film unit is to provide regions designated 58 (and by stippling) in FIG. 5 in which end portion 28vof binding element 20 is not adhered to end marginal portion 34 of photosensitive sheet 12. Regions 58 in which the binding element and sheet l2 are not sealed together extend from the trailing edge of sheet l2 toward the leading end of the film unit to the edge of opening 22 in the binding element and provide a path for air to escape from the film unit during spreading of the processing liquid. To facilitate the escape of air between the trailing edge of sheet 12 and binding element 20, notches are formed in the trailing edge portion of sheet 12 underlying unsealed regions 58 and communicating therewith. The construction of the film unit and of the pressure-applying member, e.g., rolls 46, employed to spread the processing liquid are such that any air between the sheets is advanced ahead of the mass of processing liquid and is ejected from the film unit at the trailing end thereof by passing through notches 60 between end marginal portion 34 and binding element 20 as shown in FIG. 6.'As excess processing liquid advances ahead of spread rolls 46 it moves behind the air into the spaces defined by openings 54 and, possibly, notches 60 (as shown in FIG. 7), wherein the excess processing liquid is trapped. Escape of the processing liquid via the same route is prevented by the pressure-applyin g members (rolls 46) which, at this stage of the process, engage and compress end portion 28 of binding element 20 against the surface of sheets 12 and 14 effectively sealing the unadhered regions designated 58 so that the processing liquid is unable to flow between the binding element and the outer surfaces ofthe sheets.

The present invention is intended to encompass other means for venting air from the film unit while preventing escape of processing liquid. For example, the binding element or at least the trailing end portion thereof may be formed of a porous material through which air may pass with a minimum of resistance and have pores of a size which effectively preclude passage of the viscous processing liquid. Porous materials offering little resistance to the passage of air and essentially impermeable to viscous liquids include porous polymeric film and fibrous materials commonly used as filters. Such materials may be coated with a waterproof agent to increase their impermeability to aqueous liquids without reducing their gas permeability.

Although the film unit of the invention has been described in terms of a component construction incorporating at least two selectively sensitized photosensitive strata in a contiguous relationship and specifically in terms of a tripack structure comprising red-, greenand blue-sensitive silver halide emulsions having associated therewith, respectively, cyan, magenta, and yellow dye developers, the photosensitive medium of the film unit may comprise at least two sets of selectively sensitized minute photosensitive elements arranged in the form of a mosaic screen with each photosensitive element having associated therewith, for example, an appropriate dye developer in or behind its respective silver halide emulsion portion. In general, such a photosensitive screen will comprise red-sensitive emulsion elements, green-sensitized emulsion elements and, blue-sensitized emulsion elements having associated therewith, respectively, a cyan, a magenta, and a yellow die developer.

The film unit of the invention is particularly adapted to the production of color images by a variety of additive processes and/or for the production of other visual effects including stereoscopic picturesl and cinematography. Additive color images may be produced by employing a suitable-screen in place of the transparent image-receiving sheet and for additive color photographs this screen may comprise a mosaic of minute color filter elements, for example, of the primary colors, red, green and blue, or a lenticular screen. Processes of this type are well known in the art for producing monochrome images (e.g., black and white), which, with the aid of' appropriate screens, can be exhibited in full color and/or to produce other visual effects including stereoscopic and cinematographic.

IN the Preceding description, photographic film units and processes have been described adapted to the production of positive prints either in black and white or color adapted to be viewed or exhibited by reflected light. The film units and the processes of the invention are also adapted to the production of visible images designed to be exhibited by light transmitted through the film unit; and in such an embodiment, all of the layers of the film-unit would be formed of transparent materials and the visible image may be either a positive or negative image. ln the case of a positive transfer image together with a negative image, the higher covering power of the positive image (silver) will enable the positive image to be viewed by transmitted light without any noticeable adverse effect due to the presence of the negative image.

There will be seen from the foregoing that the film unit described as embodying the invention and the process employing the film unit are made possible by the film unit construction represented by a more convenient, simplified and less expensive photographic system by which it is possible to produce high quality and aesthetically pleasing photographic prints employing novel and improved photographic apparatus. The film unit is self-contained, is readily and easily stored,

handled and processed, and the construction of the film unit l as well as the method of the invention provides for the rapid and easy expulsion of air from the film unit during spreading of the processing liquid while at the same time preventing escape of the processing liquid.

Since certain changes may be made in the above product and process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. ln a photographic film unit adapted to be processed by a viscous liquid composition distributed within said film unit from one end of said film unit toward the opposite end thereof, and comprising a photographic image-recording sheet including a support and at least a photosensitive layer on one side of said support capable of recording a photographically useful image when exposed to actinic light, a second sheet at least coextensive with said image-recording sheet and disposed in face-to-face relation thereto and a collapsible container carrying a viscous processing liquid including an agent capable, when spread in a layer between said sheets, of reacting with said photosensitive layer following exposure thereof to produce an image between said sheets, the improvement comprising:

retaining means located externally of said sheets and engaged with the marginal portions thereof for retaining said sheets in face-to-face relation throughout the entire marginal extent of said photosensitive sheet; said marginal portion of one of said sheets at said opposite end of said film unit including a plurality of spaced notches extending inwardly from the end edge of said one sheet; the quantity of said liquid contained in said container being at least sufficient to form a layer of predetermined, uniform thickness throughout substantially the entire region defined by said facing surfaces of said sheets exclusive of areas of said region underlying said retaining means; said container being located exterior of said region defined by said facing surfaces of said sheets and having sections defining a discharge passage for releasing the liquid contents of said container for distribution between said facing surfaces of said sheets; said retaining means being constructed to release gas from said region between said sheets at said opposite end of said film unit during spreading of said liquid within said region from said one end of said film unit toward said opposite end thereof and including at least a strip of substantially fluid impermeable sheet material secured around and to the outer surfaces of said marginal portions of said sheets at said opposite end of said film unit except in said regions of said one sheet extending from a transverse edge of said strip to said notches to provide passages for gas between said one sheet and said strip. 2. A method of rapidly spreading a viscous photographic 40 liquid in a continuous uniform layer within a photographic film unit comprising a pair of sheets secured in face-to-face relation at theirlateraledges and at their trailing end by a binding element of an essentially fluid impermeable sheet material adhered around and to the lateral and trailing..end 45 margins of said sheets, and said method comprising:

injecting a mass of viscous liquid processing composition between the leading end portions of said sheets; progressively applying compressive pressure to a transverse region of said sheets extending substantially from side-toside thereof and located behind said mass of liquid to advance said mass between said sheets toward the trailing ends thereof to spread said liquid in a layer between said sheets and force gas between said sheets ahead of said mass toward said trailing ends; discharging said gas from between said sheets at said trailing ends thereof while directing said gas between said trailing end margin of one of said sheets and said binding element adhered thereto at regions of said binding element in which the latter is not adhered to said one sheet; and as said mass of liquid approaches said trailing edges of said sheets compressing said binding element against said one sheet to prevent escape of said liquid from between said one sheet and said binding element. 3. The method defined in claim 2 wherein compressive pres- 65 sure is progressively applied to said sheets in a transverse region ahead of said mass of liquid to expel gas from between said sheets ahead of' said mass of liquid. 

2. A method of rapidly spreading a viscous photographic liquid in a continuous uniform layer within a photographic film unit comprising a pair of sheets secured in face-to-face relation at their lateral edges and at their trailing end by a binding element of an essentially fluid impermeable sheet material adhered around and to the lateral and trailing end margins of said sheets, and said method comprising: injecting a mass of viscous liquid processing composition between the leading end portions of said sheets; progressively applying compressive pressure to a transverse region of said sheets extending substantially from side-to-side thereof and located behind said mass of liquid to advance said mass between said sheets toward the trailing ends thereof to spread said liquid in a layer between said sheets and force gas between said sheets ahead of said mass toward said trailing ends; discharging said gas from between said sheets at said trailing ends thereof while directing said gas between said trailing end margin of one of said sheets and said binding element adhered thereto at regions of said binding element in which the latter is not adhered to said one sheet; anD as said mass of liquid approaches said trailing edges of said sheets compressing said binding element against said one sheet to prevent escape of said liquid from between said one sheet and said binding element.
 3. The method defined in claim 2 wherein compressive pressure is progressively applied to said sheets in a transverse region ahead of said mass of liquid to expel gas from between said sheets ahead of said mass of liquid. 